Sustained release dosage forms have found wide usage in a variety of technology areas, such as in personal care or agricultural applications, water treatment and particularly in pharmaceutical applications. Sustained release dosage forms are designed to release a finite quantity of a compound into an aqueous environment over an extended period of time. Known sustained release pharmaceutical dosage forms contain a medicament or a vitamin whose rate of release is controlled by a polymeric matrix. Sustained release pharmaceutical dosage forms are desirable because they provide a method of delivering a long-lasting dose in a single application without overdosing. U.S. Pat. No. 4,734,285 discloses that the release of an active composition from a solid tablet can be prolonged by employing a fine particle sized hydroxypropyl methylcellulose ether composition. The particle size of the hydroxypropyl methylcellulose ether is so small that at least 90 percent by weight of the cellulose ether particles pass through a 100 mesh screen, and preferably at least 97 percent by weight of the cellulose ether particles pass through a 140 mesh screen to achieve a long release profile. The fine particle size of the hydroxypropyl methylcellulose ether compositions can be achieved using a ball mill for grinding the hydroxypropyl methylcellulose ether compositions. While excellent sustained release profiles are achieved when incorporating the ball milled hydroxypropyl methylcellulose ether into the pharmaceutical dosage form, it is difficult to precisely control the sustained drug release profile using a ball mill. Hydroxypropyl methylcellulose ether batches that do not meet the desired sustained release profile have to be reprocessed or used for other purposes.
Accordingly, it would be desirable to find another way of controlling or adjusting the release of an active ingredient from a dosage form.